When Yanagawa and Isshin entered the Research and Development Institute, the wide corridors were no longer lined with traditional squad rooms.
Instead, both sides were filled with independent laboratories, separated by high-strength transparent materials or special force fields.
Researchers in white lab coats coated with anti-contamination reishi layers moved busily about, many wearing strange goggles, masks, or other auxiliary devices.
Some stood at workstations, performing complex calculations on floating reishi models.
Some recorded data from bizarre biological samples suspended in culture tanks.
Others were conducting physical collision experiments that looked dangerous at a glance.
Noisy.
Busy.
Messy.
And yet, beneath it all was a warped kind of efficiency and obsession.
This place did not have the discipline common to other Gotei 13 divisions.
What replaced it was the absolute pursuit of knowledge, and the reckless exploration of the unknown.
Occasionally, a researcher clutching a board covered in insane formulas hurried past, paying no attention whatsoever to Yanagawa or Isshin.
“Tch.
Every time I come here, it feels like I’ve wandered into another world.”
Isshin covered his nose and dodged a cloud of purple smoke that sprayed from a nearby vent.
After stating their identities, they were led deeper into the institute by a researcher with vacant eyes but unnervingly precise movements.
The laboratories here were larger, and the protective measures far stricter.
The concentration of reishi in the air was so high that it made their skin tingle faintly.
At last, they arrived before a massive metal door engraved with complex sealing runes, its style exaggerated and unsettling.
The door opened, revealing an enormous space within.
Countless instruments, test tubes, culture tanks, mechanical wreckage, biological specimens, and screens filled with mad data were scattered everywhere.
At the center of the room stood a cylindrical transparent container filled with unknown green liquid.
Something unusual seemed to be sealed inside.
The sound of bubbling liquid echoed through the air.
And the master of this place, Twelfth Division Captain Mayuri Kurotsuchi—stood with his back to them before a massive control panel.
His hands moved at speeds almost impossible to follow, operating countless buttons, levers, and floating screens.
From his mouth came an excited, shrill chuckle.
“Yes… exactly like that!
Show me where your limits lie, Experimental Subject 247!”
He yanked down a lever.
The green container at the center of the room suddenly twisted and swelled violently.
Spiderweb cracks spread across its surface.
“Captain!
Spiritual pressure overload!
It’s going to explode!” a thin-voiced officer wearing a blast-resistant mask cried out.
“Explode?
No!
This is evolution!”
Mayuri laughed wildly.
Rather than stopping it, he slammed another red button.
Boom!
The container finally gave out and burst apart.
Thick green fluid and violent reishi turbulence splattered outward, only to be blocked completely by a spiritual barrier that rose instantly before the control panel.
When the smoke cleared, all that remained was a small, dim pile of charred-looking dust.
“Tch.
Failed again.
Still not enough tolerance.
Next time, perhaps I’ll add Gillian-class reishi…”
Mayuri showed no discouragement whatsoever.
Instead, he stroked his chin, the eyes behind his mask gleaming with even greater fanaticism.
Only then did he seem to notice the two visitors at the door.
He slowly turned around.
His gaze locked onto Yanagawa like a scanner, and he let out a curious “Oh?”
“Rare guests indeed.”
Mayuri’s voice was sharp and slick.
He spread his arms in an exaggerated welcoming gesture, though the motion felt more like showing off his lair.
“Sir Yanagawa of the Royal Guard… and Captain Shiba of the Tenth Division.
What wind has blown the two of you into my humble little laboratory?”
“Could it be that you’re interested in the failed experiment just now?
It may have failed, but the data is valuable.
Care to take a look?”
His words came rapidly, jumping from one thought to another.
“Captain Kurotsuchi,” Yanagawa said, ignoring both the dangerous surroundings and Mayuri’s eccentric behavior.
He went straight to the point.
“Forgive the intrusion.
We came hoping the Research and Development Institute could assist in creating a special tool for the investigation of the ‘Twin Hyōrinmaru’ incident.”
“Oh?
A special tool?”
Mayuri’s interest was clearly piqued.
He paced closer.
“Let me hear it.
Could it be… you want me to replicate a Hyōrinmaru? Enjoying the story? Read on at g.com.
Challenging, certainly, but not impossible.”
“As long as I have sufficient reishi samples and foundational forging data from that famous Sword God…”
“I am not asking you to replicate a Zanpakutō,” Yanagawa interrupted, cutting off that dangerous line of thought.
“I need a Tenshintai.”
The moment the word was spoken, the air in the room seemed to freeze.
Even Nemu Kurotsuchi, who had been standing quietly nearby, lifted her head almost imperceptibly.
Mayuri stopped moving.
The gaze behind his mask became razor-sharp, even cold.
He slowly straightened and drew out a meaningful, unreadable sound.
“Hmmm?”
“The Tenshintai.
One of the little toys Kisuke Urahara left behind.”
Mayuri’s voice remained shrill, but now carried an indescribably complex tone.
“A device that forcibly drags the dull true form of a Zanpakutō into reality for pretend play.
What, Sir Yanagawa?
Are you interested in those old relics Urahara left behind?”
He did not agree or refuse at once.
Instead, he slowly circled Yanagawa as if evaluating a rare specimen.
“Creating a Tenshintai would not be difficult for me.”
“The research notes Kisuke Urahara left behind were chaotic, filled with personal quirks, tasteless encryption, and utterly unaesthetic formatting.”
“But I cracked the core principles and technical details long ago.
Optimized them, even.
In some respects… surpassed them entirely.”
His tone made no effort to hide his disdain for Urahara’s research style, yet it also carried an almost obsessive pride.
“However…”
Mayuri shifted tone, stopping before Yanagawa.
His eyes fixed on him through the mask.
“Why should I help you?
The Royal Guard title alone is not enough to make me, Mayuri Kurotsuchi, Captain of the Twelfth Division and President of the Research and Development Institute, lower myself to reproduce some limited-use old toy left behind by a predecessor I have already surpassed.”
“Unless…”
He raised one long finger.
“You can provide something interesting in exchange.
For example, cooperating with me on certain special research.
Or perhaps… the true reason why you gained the favor of the Royal Guard?”
His demand was direct, greedy, and full of probing intent.
Clearly, he was deeply interested in Yanagawa himself, and in the Royal Guard.
Yanagawa suddenly turned toward Isshin, who was looking around uneasily at the bizarre laboratory.
An idea occurred to him.
“Captain Isshin,” Yanagawa said in a grave tone.
“Huh?
What is it, Yanagawa?” Isshin answered instinctively, a bad feeling rising in his chest.
Yanagawa sighed, as if making a difficult decision.
“At this point, in order to obtain the Tenshintai as quickly as possible, uncover the truth, and save your future subordinate Tōshirō Hitsugaya…”
“I’m afraid we may have to trouble you.”
“Trouble me?
What’s that supposed to mean?” Isshin froze.
Yanagawa pointed toward Mayuri, who was watching them with growing interest, and said in a “pained” voice:
“Captain Kurotsuchi will expend manpower and resources to create the Tenshintai.
In exchange, he requires a ‘volunteer.'”
“Someone to cooperate with the Research and Development Institute on certain… special experiments.”
“Captain Isshin, as the Captain of the Tenth Division, you possess powerful spiritual pressure, extensive experience, and you are Hitsugaya’s future superior.
By reason and by sentiment, this important task belongs to no one but you.”
Cooperate with research?
At the Research and Development Institute?
Serve as Mayuri Kurotsuchi’s “volunteer”?
Isshin’s eyes widened as if he had just heard the most terrifying joke in the world.
His imagination immediately produced an image of himself strapped to an operating table, surrounded by cold surgical instruments and bubbling unknown fluids, while Mayuri approached with a huge syringe and a pair of slime-covered gloves, cackling horribly.
“Hiss—!”
Isshin sucked in a sharp breath.
Cold sweat instantly soaked his back.
He leapt away from Yanagawa and pointed at him, his voice changing pitch.
“Hey!
Yanagawa!
You bastard!
You don’t sell out teammates like this!
You’re handing me over to Mayuri for research?!
No way!
Absolutely not!
I’d rather die!”
His reaction was intense—arms waving, face filled with fear, rage, and disbelief at the betrayal.
Yanagawa remained perfectly composed, looking at Isshin with an expression that seemed to say, This sacrifice is necessary for the greater good.
Isshin cursed for a while, but Yanagawa showed no reaction.
Meanwhile, Mayuri seemed increasingly interested in the “proposal,” and Isshin’s heart sank.
He looked at Yanagawa’s righteous face, then thought of Tōshirō Hitsugaya—still imprisoned by Central 46, future uncertain.
The genius boy whose division application he had already quietly prepared…
A surge of hot-blooded emotion mixed with helplessness and tragic resolve welled up within him.
Isshin gritted his teeth, his internal struggle plain on his face.
He grabbed at his hair and groaned in pain.
“Damn it… Yanagawa, you bastard.
You win!”
As though using every ounce of strength he had, he forced the words out through clenched teeth, wearing the expression of a man walking to the execution ground.
“For Shiro… I’ll do it!
It’s just research cooperation, right?!
Come on, Captain Kurotsuchi!
Use whatever methods you want!
If I so much as flinch, I will bury myself!”
He puffed out his chest and closed his eyes, looking like a martyr ready to be carved up.
Only his trembling eyelids and clenched fists betrayed the terror inside him.
But the expected delighted cackle from Mayuri never came.
Instead, there was a blatant snort of disdain.
“Hmph.”
Isshin opened one eye in confusion.
Mayuri was waving his strangely gloved hand dismissively, his voice dripping with contempt.
“Isshin Shiba?
Research cooperation?
You?”
He looked Isshin up and down as though appraising an ordinary rock.
“Plain captain-level spiritual pressure.
A completely unremarkable Zanpakutō ability.
Not even the slightest noteworthy mutation or special talent.”
“Dissecting you would yield less useful data than one of my randomly raised Gillian-class Hollow variants.
A waste of my time.
A stain on my instruments.”
“…”
Isshin froze.
The tragic expression on his face stiffened, then slowly cracked apart.
A strange feeling welled up in him.
Relief?
Or humiliation at being so thoroughly dismissed?
I’m the Captain of the Tenth Division.
Head of a branch family of one of the Five Great Noble Houses.
And I’m not qualified to be experimental material?
Even Yanagawa’s mouth twitched almost imperceptibly.
He had not expected Mayuri to respond that way either.
Still, this was convenient.
It saved him from actually selling Isshin off.
Mayuri ignored the heavily wounded Isshin and turned his attention back to Yanagawa.
After that little interruption, he seemed to have a new idea.
He tilted his head slightly, his bone-like mask making a faint scraping sound.
“However, Sir Yanagawa…”
His tone became interested again, now carrying a faint, almost nostalgic quality.
“Since you will soon be going to the Royal Palace and becoming a member of the Royal Guard… perhaps I could ask you for a small favor.”
“Please speak,” Yanagawa said.
“There is an old superior of mine among the Royal Guard,” Mayuri said slowly.
“Kirio Hikifune.
Former Captain of the Twelfth Division.
Founder of the theories behind Gigai and Artificial Souls.”
“If you meet her in the Royal Palace, give her my regards.”
Yanagawa recalled the records he had seen in the Great Spirit Book Library.
Indeed, before Kirio Hikifune had been promoted to the Royal Guard, she had been Mayuri’s superior.
Looking at this twisted, mad scientist before him, now showing such an unexpectedly human side, Yanagawa understood.
He nodded.
“Very well.
When I meet Lady Kirio Hikifune, I will convey Captain Kurotsuchi’s regards and current situation.”
After they left the Research and Development Institute, Isshin finally breathed a full sigh of relief.
He wiped nonexistent cold sweat from his forehead and muttered to Yanagawa with lingering fear:
“You scared the hell out of me.
I really thought I was going to be left behind for research…”
“Yanagawa, next time you make a joke like that, warn me first.”